In the field of cellular mobile radio systems, different technologies and numerous standards exist. The currently most widely used systems, i.e. second-generation systems, such as GSM (Global System for Mobile communications), are currently being complemented, and will increasingly become so in the future, by new types of mobile radio systems such as third-generation systems, like UMTS (Universal Mobile Telecommunication Network), or fourth-generation systems that are still being defined, or by new broadband Wireless LAN (Local Area Network) systems.
Current second-generation cellular networks are mostly designed to offer voice service, whilst third and fourth generation are conceived to offer a new series of data and multimedia services as well. It is foreseeable that new cellular networks will not completely replace the second generation networks currently existing and commonly used, but rather will complement them.
Thus, the networks resulting from the integration of available technologies will be able to provide clients with the ability to use new services, in addition to the usual voice service. The integration is made possible by the characteristics of the new standards, defined in such a way as to allow the new systems to be used jointly and in synergetic fashion with current cellular networks. Within the 3GPP (3rd Generation Partnership Project) standard, which defines the characteristics of the UMTS system, are specified, for instance, different procedures that enable the UMTS network to interwork with the GSM network.
In particular, the standards 3GPP TR25.881 “Improvement of RRM across RNS and RNS/BSS, Release 5”, and 3GPP TR25.891 “Improvement of RRM across RNS and RNS/BSS, Release 6”, define the functional models and the network architectures within which the CRRM algorithms are applied.
A clear market trend is the use of Wireless LAN (WLAN) technologies within a limited region of territory (called “hot-spot”) to offer broadband access to users characterised by limited mobility.
In general, Wireless LAN systems are limited to providing access to telecommunication services in a circumscribed region of territory. Consequently, they do not have a complex architecture like the one that characterises mobile radio networks (GSM or UMTS).
Wireless LAN technologies can be used within a mobile radio network in the access segment. For this reason, in the specifications of the different systems, both mobile radio and Wireless LAN, a series of activities is currently being carried out, with the aim of defining the most suitable interworking mechanisms IEEE 802.11 or HIPERLAN2) for access to the third generation mobile radio transport network.
The document of the standard 3GPP TR 23.934 “3GPP system to Wireless Local Area Network (WLAN) Interworking—Functional and architectural definition”, Release 6, specifies, for example, the functional requirements that must be met by the different network architectures that include the Wireless LAN accesses of the IEEE 802.11 in the UMTS network. Similarly, the document of the standard ETSI (European Telecommunication Standards Institute) TR 101.957 “Broadband Radio Access Networks (BRAN); HIPERLAN Type 2; Requirements and Architectures for Interworking between HIPERLAN/2 and 3rd Generation Cellular systems” specifies the interworking mechanisms of the broadband Wireless LAN standard, called HIPERLAN2, with the UMTS network.
Multi-mode mobile terminals (such as cellular telephones, personal digital assistants (PDA), connectivity cards for personal computers, etc.), designed to be able to use the different available technologies are already present in the market, and will be available in ever greater numbers in the years to come. These mobile terminals therefore are not constrained to work with a single network (i.e., following a single standard), but can indifferently use different systems, based on different standards. An example in this sense is provided by the “multi-mode” devices that are already able indifferently to handle the GSM, UMTS and Wireless LAN 802.11b standards.
Through appropriate mechanisms, it is also possible to enable a service already ongoing on a system to be transferred on another system. A method to manage the procedure for transferring a service already ongoing from one system to another is described, for example, in the document WO-A-3/069938.
At the time a request is made for a certain type of service capable, for its characteristics, of being delivered through different access systems (GSM, UMTS or Wireless LAN), it is possible to select the system to use according to considerations of opportunity and global efficiency of the multi-access network.
Within a context like the one described above, an operator of a network who uses the GSM and UMTS technologies and the Wireless LAN hot-spots is faced with the problem to be able to use, in integrated and synergetic fashion, all the resources offered by these systems to maximize the overall efficiency and the exploitation of the telecommunications network.
This context of application therefore presupposes the existence of criteria for common radio resource management (CRRM) to determine, case by case and according to the type of service requested by the user, which policy to follow to select the system that is best suited to offer the service and which criterion to apply to achieve the established efficiency targets.
The different standards mentioned above specify only the architectures, procedures and mechanisms for the interworking of the different systems, including the initial selection of which system to use when a service is requested.
However, the standards leave open the choice of the most appropriate criterion to use these tools in an effective and efficient manner.
In principle, remaining within the scope of the network architectures and interworking tools made available by the different standards, different common radio resource management methodologies, more or less valid, can be adopted.
In general, the requests that reach a network are not of a single type (e.g. only voice), but of different types (e.g. voice, streaming/interactive data characterized by different bit rates, etc.).
To take this situation into account, one can decide a priori to set a certain quantity of resources to manage exclusively a specific service. However, this “rigid” choice may not be advantageous if one wants to prevent the emergence of the situation in which new requests for a certain service can no longer be satisfied, as a result of the complete occupation of the resources dedicated to it. This is also true when, as a whole, the multi-access network would in fact still have available resources (which were devoted a priori to the exclusive use of another service).
In the more general case, therefore, it is preferable that the different services, even if they are of different types, could occupy the same set of radio resources, made globally available by the individual systems that compose the multi-access network.
For example, in the case of the GSM system, single radio “channels” (identified by the frequency and the time-slot used), can be employed both to manage a voice user, and to manage one (or more) data users (also for different types of data services).
By the same token, with the power available in a cell of the UMTS system in downlink, and with the power the mobile terminals can transmit in uplink, users requiring different services can be managed, until reaching a total limit interference level.
The different services, according to their characteristics, require a different quantity of radio resources necessary for their management.
The available resources of the multi-access network can be used for a service as well as for another. Choosing to exploit the available radio resources to manage any one of the considered services, without setting aside, a priori, a part of these resources for the exclusive use of a specific service, the resources of the multi-access network can be exploited more flexibly and efficiently, provided that suitable arrangements are adopted. In this situation, particular attention must be paid to the selection of the most suitable system to manage the service request reaching the network.
Currently, there are some known general methods which the CRRM algorithms can use to select a system over another, as suggested in Chapter 8 of the Doctoral Dissertation of Royal Institute of Technology, Stockholm (May 2003): “Radio Resource Sharing and Bearer Service Allocation for Multi-Bearer Service, Multi-Access Networks” (as of the date of filing of the present application, the dissertation in question is available at the address www.s3.kth.se/radio/Publication/Pub2003/af_phd_thesi_A.p). These methods use, for example, a predefined list of priorities, as suggested in WO-A-02/32160, to be associated to the different cases that may arise or contain a predefined selection criterion, which may vary according to the characterstics of the service under consideration. Allocation criteria are based on the characteristics of each service (such as the service class, the transfer rate to be guaranteed, the maximum requirements in terms of transfer delay and jitter) and on the loading state of the network when the new request arrives.
These methods try to assign, on each occasion, the access system that is best suited to meet the quality requirements of each type of service.
The Applicant has noted that a characteristic shared by the aforementioned methods is that they take into consideration the individual request for services that reaches the network at a given moment, neglecting the different types of service which may be requested at different instants.
Therefore, the application of these methods can lead to situations in which, to accommodate a new request for a certain service, specific network resources are used, even when not strictly necessary; this is to the detriment of subsequent requests for other types of service which, due the different intrinsic characteristics, could exclusively use the resources already allocated for the first considered service request.
In other words, taking on the management of a single request at a time, and not adopting any dynamic arrangement, prior art methods implement allocation criteria that strongly depend on the particular time sequence of the requests reaching the network.
The management of a service request at any given time, is a function of the allocations already made previously, because they determine the total loading state of the multi-access network at the time when the new request is managed. Thus, the criteria adopted by prior art methods, imply a FIBS type of logic (“First In, Best Served”).
The above substantially also applies to the solutions described in the documents WO-A-02/32160, WO-A-02/32179, WO-A-02/054677, and JP-A-2001352576, solutions in which the allocation selection is made according to individual requests, taking into account only current state of the network.